Many kinds of feedback automatic control or regulating devices have been disclosed, each serving an individual purpose and, due to the different construction they have, their usage is limited. They hardly can cope with the requirements of various automatic regulation and process control called for, and therefore, to meet different purposes, various designs and selections shall have to be provided. It is quite inconvenient both in manufacturing and use. Furthermore, under normal operation these kinds of devices would often give unexpected errors beyond limit, and very often temporary abnormal variations result due to change of load conditions, sometimes due to the slow response, a desired precise and stable control cannot be easily achieved. To overcome the aforementioned drawbacks, a device that is capable of detecting the said error or variation to keep balance within a small range of errors is urgently needed. But the complexity of the improved design usually makes the device hard to operate. In the meantime, the use is still limited, and most of the designs can only serve for the control of small range physical quantities, therefore far from ideal.